1. Field of the Invention
The present invention relates to a disk chucking device for holding a magnetic disk or an optical disk, which has a doughnut shape and a central hole, to a disk drive device in inspection devices or disk holding devices.
2. Description of the Related Art
The above-mentioned disk is automatically loaded to or removed from the disk drive device in the inspection devices using a disk mounting device, i.e., a robot hand. The disk drive device is provided with a disk chucking device for holding detachably the disk to a rotational position.
In addition, the disk is held in the disc chucking device in a film forming step, a cleaning step, an etching step, etc. during a disk production process.
As shown in Patent Document No. 1, conventional disk chucking devices have used a C-shaped chucking ring as a means for holding a disk by being fit into the central hole of the disk.
The C-shaped chucking ring wraps a C-shaped spring. The disk can be held by spreading the C-shaped chucking ring against the biasing force of the C-shaped spring, and contacting the C-shaped chucking ring to the inside of the central hole of the disk with pressure. The disk can be released by closing the C-shaped ring using the biasing force of the C-shaped spring, and releasing the contact between the C-shaped chucking ring and the central hole of the disk.
In addition, the disk chucking device of Patent Document No. 1 also has a circumferential cam which goes up and down along the central axis of the central hole of the disk to spread and close the C-shaped ring. Furthermore, the disk chucking device uses an air chucking system which makes the circumferential cam go up to release the hold of the disk by the C-shaped chucking ring and makes the circumferential cam go down to hold the disk by the C-shaped chucking ring.
More specifically, the disk chucking device of Patent Document No. 1 uses a structure in which the circumferential cam is provided to a top end of a shaft, and the circumferential cam is always biased downwardly by a spring having a downward biasing force.
When an air force (positive pressure) is applied to a lower surface of a diaphragm provided in the bottom end of the shaft, the shaft and the circumferential cam go up along their axis while resisting the downward biasing force of the spring. While going up, the C-shaped chucking ring is released from the inner surface of the central hole in the disk, and closes to release the disk.
In contrast, when the air force applied to the lower surface of the diaphragm is removed, the shaft and the circumferential cam go down along their axis by the downward biasing force of the spring. While going down, the C-shaped chucking ring spreads due to its resilience, and thereby the C-shaped chucking ring presses to and holds the inner surface of the central hole in the disk.
Patent Document No. 2 discloses a disk chucking device having plural chucking clicks in which the chucking clicks are inserted inside of the central hole in the disk, and the gaps between the chucking clicks are spread to hold the disk from the inside of the central hole.
[Patent Document No. 1] Japanese Unexamined Patent Application, First Publication No. H06-314456
[Patent Document No. 2] Japanese Unexamined Patent Application, First Publication No. 2007-102959
In the disk chucking device using the air chucking system, since an air actuation mechanism for operating the C-shaped chucking ring and the circumferential cam have to be stored in the disk driving device, the disk drive device is larger, and complicated. In addition, a spindle motor, which is a driving force for the disk drive device and forms a joint of the air flow, is large and extremely expensive.
In addition, it is difficult for the C-shaped chucking ring and the C-shaped spring to be elastically displaced with a uniform curvature factor in the whole circumference because they are C-shaped. Furthermore, a difference between elastic displacement amounts in the C-shaped chucking ring and the C-shaped spring is easily generated. Therefore, it is difficult to uniformly contact the C-shaped chucking ring to the inner surface of the central hole in the disk with pressure. As a result, it is also difficult to rotate stably the disk at high speed. Furthermore, when the inner surface of the central hole in the disk is pressed non-uniformly, it causes strain or deformation of the disk, and degrades the reliability of inspections.
When the C-shaped chucking ring spreads, cutout portions of the C-shaped spring may scratch the surface of the C-shaped chucking ring. In addition, the cutout portions of the C-shaped spring slide on the surface of the C-shaped chucking ring, and generate dusts have make adverse effects on the inspection of disks. Furthermore, when dusts are generated during a production process of a disk, the dusts may be contaminated in a film formed on the surface of the disk, and may degrade the film properties.
In addition, when the holding force is increased to hold the disk during rotation at high speed in the disk chucking device, in which a disk is held by inserting the chucking clicks through the central hole of the disk and spreading the gap between the chucking clicks, the chucking clicks may scratch the inner surface of the central hole in the disk.